MAGNETIC-RESONANCE-IMAGING OF THE KNEE - DOES FOOT RESTRAINT IMPROVE THE EXAMINATION

Involuntary movement by the patient can cause severe artefacts in magn etic resonance imaging of the knee. We have designed and constructed a device that immobilizes the foot, and thereby the knee. In this way t he knee still remains accessible for the application of a variety of s urface coils. A retrospective subjective analysis was performed of the magnetic resonance images from a control group of 23 patients who wer e examined without the restraint device and a study group of 26 patien ts in whom the device was used. The differences in the central tendenc y of subjective scores between the control and study groups were not s ignificant for either motion artefact or anatomical conspicuity. Howev er, in terms of dispersion the observed reduction in the study group w as significant for anatomical conspicuity (p < 0.05) and almost signif icant for motion artefact (p < 0.10). These findings suggest that the restraint device may improve image quality by eliminating some of the worst motion artefacts. The device also significantly improves positio ning of the knee in relation to the magnet isocentre (p < 0.01).